The $411,700 study by the U.S. Army Corps of Engineers will also look at how much the federal government will need to pay to renourish Georgia's most popular public beach with sand.

The government has pumped millions of cubic yards of sand onto the 3.5-mile island since the 1970s, when it began renourishing the beaches on Tybee Island east of Savannah. Tybee city officials have to lobby the federal government to pump more sand every seven years.

The 2007 study will try to measure how much the Savannah River, which meets the Atlantic Ocean at Tybee Island's northern shore, disrupts the natural flow of sand being eroded and redeposited by waters along the beach.

"There is nobody who says the channel doesn't affect Tybee," said Lou Off, chairman of the Tybee Island Beach Task Force. "But there has never been an exact study to say how much it affects Tybee."

Tybee Island city officials and the Corps of Engineers are scheduled to sign an agreement next week to begin the study. The final report will have to be submitted to Congress for approval.

The study will use data going back to 1865 to track how sand moves along Georgia's 100 miles of coastline, said Daniel Parrott, chief of civil programs and project management for the Corps' Savannah District.

After that work is done, probably by July, the Corps of Engineers could take up to two years to finish the study's second phase -- determining the best way to replenish sand on Tybee Island for the least amount of money.

The next scheduled beach renourishment for the island, in 2008, is expected to cost $10 million. The federal government covers 60 percent of the cost, with state and local governments paying the rest.